Electric fuses and releasable connectors



1952 A. G. H. OXLEY E1 AL ELECTRIC FUSES AND RELEASABLE CONNECTORS FiledApril 27, 1948 w r F I nventors A tlorneyg ATI'hUTG H 0x, and DouglaA-\\ OX 7 6 Md .stituting a spare fusecarrier.

Patented Jan. 22, 1952 UNITED STATES PATENT OFFICE ELECTRIC FUSES ANDRELEASABLE CONNECTORS Arthur Guy Herbert Oxley, Banbury, and DouglasArthur James Oxley, near Banbury, England Application April 27, 1948,Serial N0. 23,506 In Great Britain August 1, 1947 4 Claims. 1

not exclusively, to releasable connectors for high voltage electricfuses or cut-outs 01' the spring- -separated type.

1 a One feature of this invention concerns the removal and replacementof a fuse link. In this type of fuse, after a fault has been cleared, itis necessary to remove the blown fuse link and replace it with a newone. This has most commonly been performed in the past by returning thecomplete fuse carrier to the makers and sub- Naturally, this involvesthe user in keeping a stock of spare fuse carriers, which is generallyundesirable, especially if a number of different types or sizes areemployed. Proposalshave therefore been made to .provide an arrangementin which the new fuse .link can be inserted in the fuse carrier by the.user. One object of the present invention is to.

providea particularly simple and convenient solution to this problem.

According to one feature of the present invention, a fuse of thespring-separated type includes releasable connecting means comprisingtwo parts to be mechanically connected together, movable towards andaway from each other in the directions of insertion and withdrawalrespectively,

including means for connecting them engaged by a spring acting in thedirection of withdrawal and released by relative movement of the partsbeyond their normal position in the direction of insertion, and delaymeans such as a dash-pot serving to delay the action of the spring andpermit withdrawal if performed with sufficient rapidity.

vention a fuse of the spring-separated type includes a releasableconnector comprising male and female parts to be mechanically connected,

whereof the female part includes a chuck comprising a cylinder having abore with a cylindrical portion and a tapered end portion, jaws havingouter conical surfaces corresponding to and engagingthe tapered portionof the cylinder bore,

a piston in the cylindrical part of the bore and Tabuttingthe ends ofthe jaws, the lit of the piston in the cylinderbeing such as to slowdown the closing of the jaws and permit the male part o 2, I theconnector to be withdrawn promptly after being moved beyond its normalposition in the direction of insertion to open the jaws.

The male portion may have circumferential rooves or aiscrewthre a'd cutin its surface to enable the jaws to hold it firmly againstunintentional withdrawal.

Although primarily designed for a fuse of the spring-separated type, theimproved connecting means may be employed for any purpose requiring areleasable connector, for which it is suitable.

In one form of the arrangement, each of the terminals at opposite ends'of the fuse link is formed at its end remote from the separating springfor engagement, by screw threads or otherwise, by an inserting andwithdrawing tool, so that either a complete fuse link or one end of aparted fuse link can be inserted into 'or withdrawn from the carrier.

The terminal of the fuse link remote from the separating spring ispreferably formed for engagement by a split collar which seats in theend contact of the fuse carrier, and when applied to the fuse linkterminal after the separating spring has been extended, holds thatcontact in its proper position in the fuse carrier.

The invention may be carried into practice in Various ways, but onespecific embodiment will be described by way of example, with referenceto the accompanying drawings, in which Figure 1 is a sectional elevationof a liquidfilled fuse embodying the invention; and

Figure 2 shows a withdrawing and inserting tool for use with the fuse ofFigure 1.

In the particular embodiment shown in Figure 1, the invention is appliedto a high-voltage liquid-filled fuse of known type, contained in anouter heat-resisting glass tube A having metal contact ferrules B and Csecured at each end. Each contact ferrule is of circular cross-section,with a pair of parallel and opposite flat surfaces formed on its sides,by means of which the fuse is held in the usual fixed contacts D and Dshown in broken lines in Figure l. The tube A is normally arrangedsubstantially vertically with a fuse link in the upper end.

.An upper terminal E of a fuse link E is mechanically supported by andelectrically connected to the upper ferrule B, while a lower terminal Eof the link is subjected to the pull of a strong Phosphor bronze.helical separating spring F, the lower end of which is secured to thelower contact ferrule C. The spring F is shunted by a tinned copperflexible conductor F which carries the current. The tube A is filledwith an arc extinguishing liquid such as carbon tetrachloride, and thelower terminal E of the fuse link is surrounded by a liquid guide orloose-fitting piston nozzle E which directs a jet of liquid into thepath of the arc.

The element E of the fuse link E comprises a relatively high-resistancewire E of high tensile strength, which takes the tension of thespring'F, and, shunting the wire E a loop of wire E of silver whichnormally takes practically all the current.

The upper end of the separating spring F is secured to a chuck G whichforms the .female member of a releasable connector. The lower end of thefuse link terminal E is formed with pin E having circumferentialrings'or a screw thread on its surface and a tapered shoulder E at itsupper end where it joins the body of the terminal. The pin E forms themale member of the connector, and-isirecei-ved by the chuck G. Eachterminal E and E is formed near its upper end with-a male screw thread,so that it can be engaged by an inserting and withdrawing tool shown inFigure 2 and described later.

The chuck G comprises a cylinder G having a bore with a lowercylindricalportion G and an upper conical portion-G Within the latterare two or more jaws G having'ou'ter-conical surfaces corresponding withthe conical portion G of the bore, whilebeneath the jaws, within thecylindrical portion G of the bore, is a piston G which bears againsttheunder side of the jaws, and bene'ath the piston isa compression springG6 which urges the piston and jaws upwards towards the 'taperedend "ofthe bore and thus tends to close 'theijaws. Apin E passes diametricallythrough "the lower part of the body of the lower terminal E, with itsends projecting :on each side of the terminal. These projecting ends canengage corresponding "slots cut in the upper edge of the conical "part Gof "the chuck'G when the terminal'i'sfpressed'fully down into the chuck:rotation of the terminal will thus be prevented and the inserting'andwithdrawing tool referred to above can easily be screwed onto the lowerterminal The piston has a recess in its upper surface to accommodate thehead of the pin E when the latter is gripped'by the jaws. The fit-of thepiston G in the cylinder bore G issu'ch as to provide adash-potei'fectgand to delay the'upwarrl movement of the piston underthe action of the connector springG 'to closeth'e jaws G The upper andlower "terminals E and E of the fuse link are spaced apart by a tube Eof non-combustible material, which is crimped onto the lowerpart of theuppe1-termina1.'li} and is a loose fit overthe upper partof'the lower"terminal E Abrass pin E passes transversely through the body of thelower terminal and its ends pro- *je'ct slightly from the surface of thelatter, forming a pair of lugs which co-opera'te with slots out in theedge of the tube E to prevent the termi- 'nalsE and E rotatingrelatively to each-other or closing up towards each other, and thusprevent the element E from beingdamaged.

The upper terminal E of the fuse link is supported by a split collar Esurrounded by a spring E which allows the split collar to be openedandslipped around the terminal E while the latter is screwed to theinserting and withdrawing tool. This terminal is fitted. with a shoulderE which bears .on the upper surface of the split :collar, whose outersurface is tapered to seat in a corresponding taper inside the upperferrule B of the carrier, and thus takes the tension of the separatingspring F.

In order that the fuse link may be replaced by the user and the fusecarrier closed, for example in the field, it is necessary to provide aconvenient form of seal which can be replaced by the user. The presentconstruction employs a diaphragm H of soft metal such as annealedsilver, having its marginal portion bent over and gripped between a pairof opposed conical surfaces, which are forced together axially byco-operating screw threads. Thus the upper end of the upper ferrule B isof reduced diameter and is formed with a'male screw thread B Above thisthe extreme end is tapered to form a conical seating B The diaphragm Hfits over the seating, and is bent down to lie in contact with theconical surface B by means of a co-operating conical surface J on a ringJ floating in a cap J. The cap is provided with a female screw thread J3 so as to screw onto the upper ferrule B, and a iiat inner face of thecap J presses axially on a corresponding opposed surface of theflo'atingring J so as to force it to grip the edge of the diaphragm'H.

The diaphragm H is provided with a dome H which clears the top of theupper terminal E The user, when he has .fitted "the diaphragm, pressesdown the dome with his finger until it makes contact with the top of theupper terminal E thus providing an alternative parallel electric path.Thus if the split ring E rises from its seating on account of internalpressure, the alternative electric path will tend to prevent pitting ofthe split ring or its seating.

By employing the floating ring J rather than forming the conical surfaceon the annular cap J, the advantage is obtained that the conical sur-.faces 15' and J can adapt themselves to exact alignment even if theaxes of the screw threads and conical surfaces are slightly out ofperfect alignment. Conveniently the screw thread in the cap J isundercut, and the ring J is placed in a press andslightly expanded by atool with a conical end which at the same time finishes the conicalseating J to the exact dimensions required. Thus the expanded ringcannot fall out of the cap and get lost.

Holes J are drilled in the .side .of the cap for engagement by theinserting and withdrawing tool now to be described.

Figure 2 shows a tool K designed for inserting and withdrawing a fuselink and to act as .a spanner for tightening or slacking the cap J ofthe upper ferrule.

The tool comprises a rod K having a .hole K drilled in an axialdirection in one end K3, and a female screw thread tapped on the insideof this hole. The female screw thread is designed to engage the malescrew thread at the upper .end of either fuse link terminal E or E. .Aring K is fixed to the other end of the rod K as shown in Figure 2, itsinternal diameter being .such that it will fit loosely over the outsideof the cap J .on the upper ferrule B. .A stud K projecting into theinterior of the ring engages one of the series of holes J drilled in theside of the cap J, thus transmitting to the cap the torque applied tothe tool K, to tighten or untighten the cap.

The fuse link E is arranged to be inserted by pushing it down into thechuck G and allowing the jaws G4 to grip it. Accordingly if a fuse linkE, consisting of an element E connected to upper and lower terminals Eand E which are located with respect to each other by a tube E, isscrewed into the threaded'hole K of the inserting and withdrawing tool Kand is pushed down into the chuck G, its rounded head will press thejaws G and piston G downwards against the action of the connector springG, and will tend to part the jaws. When the head has passed through thejaws, they will tend to close on the shank of the pin E". The engagementof th grooved surface of the pin with the inside surface of the jawsprovides a firm grip to prevent unintentional withdrawal.

Withdrawal of the complete fuse link E, or of the lower terminal E of ablown fuse link, is effected by pushing it down into the chuck beyondits normal position and then promptly withdrawing it. When the lowerterminal E is pushed down beyond its normal position, the taperedshoulder E bears against the upper surfaces of the jaws G and partsthem, as they and the piston G are forced downwards against theconnector spring G The dash-pot efiect provided by the piston G in itscylinder G delays the upward movement of the piston and jaws under theaction of the spring G Consequently if the fuse link is pushed down toits extreme position it opens the jaws, and an appreciable time, perhapsa second or two, elapses before they are closed again by the movement ofthe spring G' controlled by the dash-pot. This affords ample time forthe fuse link to be withdrawn.

The precise clearance between the piston G and the cylinder bore G2 willdepend upon circumstances, including the diameter of the piston, thestrength of the connector spring G and the nature of the fluid withinthe cylinder. In a particular case, it has been found that with air asthe fluid, a clearance of substantially less than a thousandth of aninch is desirable, but if the device is only operated when filled withcarbon tetrachloride, the clearance may be considerably more than athousandth of an inch. With more viscous fiuids it might be desirable toprovide grooves or holes for the passage of the liquid.

The action of the seal at the upper end of the fuse carrier will beclear from the description of its parts. The thickness of the diaphragmH is so chosen that it will withstand a substantial pressure within thecarrier but will fail at a pressure considerably below that required todamage the carrier. Consequently if the fuse blows on a relatively smalloverload, the diaphragm will remain unbroken and a pressure will buildup inside the carrier which will materially assist in arc extinction. Onthe other hand, on a heavy overload or fault current the diaphragm willburst, so as to avoid, as far as possible, damage to the carrier and toallow the carrier to be used again.

If an overload or fault current flows through the fuse, the silver wireE melts first, thus transferring the current to the high resistancestrain wire E which then also melts and allows the spring F to draw theterminals E and E rapidly apart; the lower terminal E of the fuse linkis drawn clear of the non-combustible tube E and the piston nozzle Edirects a jet of liquid into the path of the are.

The operation of replacement of a blown fuse link is particularlysimple, and is carried out with only the one simple tool K describedabove. First the fuse carrier is removed from the fixed contacts D and Dand its cap J is unscrewed, using the ring K and stud K of the tool K asa spanner if necessary. The upper terminal E of the .fuse link is thenwithdrawn with the aid of the withdrawing tool K, the split collar E isslipped off and the terminal E discarded. The with- 6 drawing tool isthen screwed onto the lower terminal E of the fuse link without emptyingthe liquid out of the carrier. The tool is then pressed downwards andpromptly withdrawn, thereby withdrawing the lower terminal E from thejaws of the chuck G. This terminal is also discarded, although in somecases the piston nozzle E may be fitted to a new fuse link. The liquidmay then be poured away if it is not fit for further use. A fresh fuselink is then screwed into the tool and inserted into the chuck to beheld by it. It is then drawn upwards, with the chuck attached to it,thereby extending the separating spring F. The split collar E is slippedover the upper terminal E of the new fuse link and is allowed to bedrawn down into position in the upper ferrule B of the fuse carrier.Finally the carrier is filled with fresh liquid if necessary, and a newdiaphragm H is placed over the upper ferrule B and secued by the cap .1.The spanner ring K of the tool may be used to tighten the cap ifnecessary. Finally, the dome of the diaphragm is pressed down to makecontact with the upper terminal E.

No claim is made herein for the particular construction forming a liquidseal, this constituting the subject matter of a separate application forpatent filed November 2, 1948, Serial No. 57,886, now abandoned, forimprovements in Liquid Seals.

What we claim as our invention and desire to secure by Letters Patentis:

l. A releasable connector comprising two parts movable towards and awayfrom one another in directions of insertion and withdrawal respectively,means for connecting said parts adapted to be released by movement ofsaid parts beyond their normal position in the direction of insertion, aconnector spring carried by one of said parts opposing such movement,and delay means comprising a liquid filled dashpot serving to delay theaction of the connector spring and permit withdrawal if performed withsufiicient rapidity.

2. A releasable connector comprising male and female parts, whereof thefemale part is in the form of a chuck having a body affording taperedsurfaces and two or more jaws having co-operating tapered surfaces andadapted to grip the male part when moved with it in the direction ofwithdrawal relatively to the body, and to release it when moved in thedirection of insertion, a connector spring carried by said chuck bodyopposing the latter movement, and delay means comprising a liquid-filleddashpot serving to delay the action of the connector spring and permitthe male part to be withdrawn promptly after being moved beyond itsnormal position in the direction of insertion to open the jaws.

3. A releasable connector comprising male and female parts to beconnected, whereof the female part is in the form of a chuck bodycomprising a liquid-filled cylinder having a bore with a cylindricalportion and a tapered conical end portion, jaws having conical outersurfaces corresponding with and engaging the tapered portion of thecylinder bore and adapted to grip the male member when moved with it inthe direction of withdrawal relatively to the cylinder, and to releaseit when moved in the direction of insertion, a piston in the cylindricalpart of the bore abutting the ends of the jaws, and a connector springin said body urging the piston towards the tapered end of the cylinderto close the jaws, the fit of the piston in the cylinder being such asto produce a dashpot effect and to slow the closing of the jaws andpermit the male part of the con- 33 in which the male partof theconnector has substantially circumferential grooves formed on itssurface to enable the jaws -to hold it firmly against unintentionalwithdrawal.

ARTHUR GUY HERBERT OXLEY. DOUGLAS ARTHUR-JAMES OXLEY.

REFERENCES CITED Tne .following references are of record in the file ofthis "patent:

UNITED STATES PATENTS Number Name Date Trumbull Nov. 14, 1893 Dyer June2, 1908 Ramsey May 9, 1933 Conrad Aug. 29, 1933 Earle Nov. 13, 1934Conrad Aug. 31, 1937 Sroka Nov. 25, 1941 Sample et a1 Nov. 9, 1943Hanrahan Feb. 20, 1945 Shafi Aug. 13, 1946

